Revert "Move assistant icon animation to CompositorAnimationOberver"

This reverts commit 33fc6c64.

Reason for revert: One or the other of this CL and https://crrev.com/c/748268 (perhaps both in combination?) broke PaletteTrayTestWithVoiceInteraction.StylusBarrelButtonActivatesHighlighter on Linux ChromiumOS Tests (dbg)(1):

https://uberchromegw.corp.google.com/i/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/31692

The connection to these voice interaction Cls seems pretty clear. I can't identify which one it is, though, so while I apologize for the trouble, I'm going to revert both to ensure that the bot turns green again.

Original change's description:
> Move assistant icon animation to CompositorAnimationOberver
> 
> BUG=None
> TEST=locally build and see animation running as before.
> 
> Change-Id: I1eb62490108beaaec0795adb4251054c03b364e1
> Reviewed-on: https://chromium-review.googlesource.com/748273
> Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#513211}

TBR=xiyuan@chromium.org,xiaohuic@chromium.org

Change-Id: I5ef677c189808601f8e357f56a171bf920b10fa0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: None
Reviewed-on: https://chromium-review.googlesource.com/749851Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513272}

ash/shelf/voice_interaction_overlay.cc

@@ -114,8 +114,7 @@ constexpr int kMoleculeOrder[] = {0, 2, 3, 1};
 
 }  // namespace
 
-class VoiceInteractionIcon : public ui::Layer,
-                             public ui::CompositorAnimationObserver {
+class VoiceInteractionIcon : public ui::Layer {
  public:
   VoiceInteractionIcon() : Layer(ui::LAYER_NOT_DRAWN) {
     set_name("VoiceInteractionOverlay:ICON_LAYER");
@@ -127,32 +126,14 @@ class VoiceInteractionIcon : public ui::Layer,
   }
 
   void StartAnimation() {
-    if (!GetCompositor()->HasAnimationObserver(this))
-      GetCompositor()->AddAnimationObserver(this);
+    animation_timer_.Start(FROM_HERE,
+                           base::TimeDelta::FromMilliseconds(
+                               base::TimeTicks::kMillisecondsPerSecond /
+                               gfx::LinearAnimation::kDefaultFrameRate),
+                           this, &VoiceInteractionIcon::AnimationProgressed);
   }
 
-  void StopAnimation() {
-    if (GetCompositor()->HasAnimationObserver(this))
-      GetCompositor()->RemoveAnimationObserver(this);
-  }
-
-  // ui::CompositorAnimationObserver
-  void OnCompositingShuttingDown(ui::Compositor* compositor) override {}
-  void OnAnimationStep(base::TimeTicks timestamp) override {
-    uint64_t elapsed = (timestamp - base::TimeTicks()).InMilliseconds();
-    for (int i = 0; i < DOT_COUNT; ++i) {
-      float normalizedTime =
-          ((elapsed - kMoleculeAnimationOffset * kMoleculeOrder[i]) %
-           kMoleculeAnimationDurationMs) /
-          static_cast<float>(kMoleculeAnimationDurationMs);
-
-      gfx::Transform transform;
-      transform.Translate(0,
-                          kMoleculeAmplitude * sin(normalizedTime * 2 * M_PI));
-
-      dot_layers_[i]->SetTransform(transform);
-    }
-  }
+  void StopAnimation() { animation_timer_.Stop(); }
 
  private:
   enum Dot {
@@ -181,6 +162,25 @@ class VoiceInteractionIcon : public ui::Layer,
     return "UNKNOWN";
   }
 
+  void AnimationProgressed() {
+    gfx::Transform transform;
+
+    uint64_t now =
+        (base::TimeTicks::Now() - base::TimeTicks()).InMilliseconds();
+    for (int i = 0; i < DOT_COUNT; ++i) {
+      float normalizedTime =
+          ((now - kMoleculeAnimationOffset * kMoleculeOrder[i]) %
+           kMoleculeAnimationDurationMs) /
+          static_cast<float>(kMoleculeAnimationDurationMs);
+
+      transform.MakeIdentity();
+      transform.Translate(0,
+                          kMoleculeAmplitude * sin(normalizedTime * 2 * M_PI));
+
+      dot_layers_[i]->SetTransform(transform);
+    }
+  }
+
   /**
    * Convenience method to place dots to Molecule shape used by Molecule
    * animations.
@@ -209,6 +209,8 @@ class VoiceInteractionIcon : public ui::Layer,
   std::unique_ptr<ui::Layer> dot_layers_[DOT_COUNT];
   std::unique_ptr<views::CircleLayerDelegate> dot_layer_delegates_[DOT_COUNT];
 
+  base::RepeatingTimer animation_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(VoiceInteractionIcon);
 };